The structure of hair and chemistry assist in defining the parameters needed to strengthen the hair during the bleaching process and color treatment. The hair structure is composed of the cuticle, cortex and medulla. The cuticle is the outer protective layer of the hair fiber, which provide the sensory and shine characteristics of hair. The cuticles physically overlap, thereby forming a shield like barrier to protect the hair from chemical, physical and environmental treatments. The cortex is the major component of the hair and is responsible for the mechanical strength. The inner most of the hair fiber is the medulla and contains much of the melanosomes, which provide hair its pigment color.
The chemistry of hair is what provides and maintains hair its structural integrity. The hair is primarily composed of proteins, lipids and water. Human hair is composed of 65-95% protein, which gives hair much of its properties, such as curly, wavy, kinky, straightness, etc. The composition of lipids in hair is 1-9%, enhancing the conditioning properties, such as flexibility, surface gloss and lubricity of hair. Lipids in the internal part of the hair provide structural reinforcement and rigidity. Water is another major component of hair. The water forms strong hydrogen bonds with proteins, thereby influencing the tensile strength, swelling, flexibility and shape of hair.
Hair bleaching requires one or more cycles of applying high concentrations of bleaching agent to permanently decolor the hair by oxidizing melanin in the cortex of the hair. The bleaching process is often highly alkaline (pH 10-13) resulting in a dramatic degradation of the structural integrity of the hair. Several products are commercially available that are promoted to enhance the quality of the hair when added to the bleaching process. For instance, US 20160206535 A1, U.S. Pat. No. 9,326,926 B2 discloses formulations, kits, and methods for rebuilding the disulfide bonds in keratin found in hair, skin, or nails. U.S. Pat. No. 9,498,419 relies on maleic acid. US2015/0034117A1 relies on maleic acid and ionic linkers that as described are preferably water soluble. Hydrophobic siloxanes are not mentioned as a possible linker in any above referenced prior art.
Hair that is damaged due to a hair coloring treatment and/or other reducing treatment, such as during a permanent wave, can be treated with the formulations containing one or more active agents. The formulations may be applied after a hair coloring treatment or simultaneously with a hair coloring treatment. Use of the active agent formulations during a permanent wave treatment prevents the reversion of the hair to its previous state for extended periods of time. The above referenced patent family discusses use of maleic acid and its salts, formulated into aqueous media. This class of ingredient is very hydrophilic and while having some activity, it is not fully reacted during the bleaching cycle, and the remainder would wash out of the hair rapidly during subsequent processing and washing.
Similar damage to the hair can also result from permanent wave treatments. In both coloring and permanent wave processes, improvements are also needed to repair damage and/or to strengthen the hair during or after such styling treatments. Additionally, improved treatments and methods are needed which can be applied to skin and nails to repair damaged keratin.
Maleic acid is commonly used as a neutralizer in cosmetic applications, however the percentage presumably used in bleaching applications would be significantly higher, most likely greater than 5% and would be outside the recommended use level reviewed by the expert panel [Int J Toxicol. 2007; 26 Suppl 2:125-30 Final report on the safety assessment of Maleic Acid.] In this cosmetic ingredient review, expert panelists discussed a study of 50 human subjects wherein maleic acid at 20% was applied to one forearm daily for a period of 6 weeks. Acute vesicular dermatitis was observed in 17 subjects, who were dropped from the study. Only five of the remaining subjects accommodated to the treatment, the rest had varying degrees of inflammation or hyperirritable skin. Although maleic acid itself may be a dermal and/or ocular irritant, its use as a pH adjustor in cosmetic formulations dictates that most of the acid will be neutralized into various maleate salts. The claims in U.S. Pat. No. 9,326,926 include the use of the free acid at a level which would be outside of the scope of the expert panel's recommendations for reviewed safe use. In cases when the maleic salts are used, the bleaching process includes neutralization steps that may incidentally create high exposure to free maleic acid which is an irritant.
U.S. Pat. No. 5,641,478 discusses the use of a cationic polymer for strengthening hair while applying the hair swelling component. This allows the cationic polymer to be affixed to the hair.
U.S. Pat. No. 6,124,490 discloses ionically cross-linked polymers that were potent thickeners that contained a PCA group paired with a secondary amine together on the same pendant group. The position could be anywhere on the molecule including the terminus of the polymer on either side or both sides. The zwitterionic nature is distinctive from a PCA group without the paired amine.
U.S. Pat. No. 8,053,513 teaches that with adding a higher degree of PCA groups, the more hydrophilic the product can become, even becoming water soluble and detergent like. For instance, the properties of 2-pyrrolidone-4-carboxylic acid substituted polysiloxanes can be dramatically altered by increasing the presence of the carboxylic acid-substituted pyrrolidone monomers on the polysiloxane. This results in enhanced detergent and solubility in water and the ability to form water-in-oil emulsions thereby providing usefulness across a broad range of formulations having enhanced electrolytic and silicone and/or hydrocarbon compatibility and cleansing properties. The general polymers described by U.S. Pat. No. 8,053,513 B2 and other related prior art are pendant-functional materials containing one or more PCA groups. The authors made no provision for PCA groups exclusively residing at the alpha-omega terminal ends of the molecule.
U.S. Pat. No. 6,730,765 B1 discloses a method for the preparation of reacting maleic anhydride with a bis-amino siloxane resulting in at least a mono-functional maleamic functionalized silicone and is also suitable for use in this invention. A similar polymer was made in accordance to U.S. Pat. No. 8,952,080, [specifically example 2 Preparation of Siloxane Macromer (B) exhibited as their structure V].